A liquefied natural gas (LNG) is in a colorless liquid state in which a natural gas containing methane as a main component is cooled at a temperature of −163° C. to reduce a volume thereof to 1/600. LNG storage tanks for storing an LNG are manufactured with a structure and material which endures an ultralow temperature for gas liquefaction.
Such an LNG storage tank, for example, has a dual sealing structure including a primary barrier, an upper heat insulation board, and a lower heat insulation board. The primary barrier contacts an LNG to primarily seal the LNG. The secondary barrier secondarily seals a leaking LNG when the LNG leaks through the primary barrier to prevent the LNG to contacting an inner hull.
The secondary barrier includes main secondary barriers and auxiliary secondary barriers. The main secondary barrier is disposed on the lower heat insulation board in parallel with the lower heat insulation board with a gap therebetween. The auxiliary secondary barrier is attached to the main secondary barriers between the upper heat insulation boards while covering a gap between the main secondary barriers. The secondary barrier may be secured in sealing property by the auxiliary secondary barriers.
In installation of the conventional auxiliary secondary barrier, an adhesive is applied to an edge of the main secondary barrier, and the auxiliary secondary barrier and a protection sheet are disposed on the adhesive. Then, the auxiliary secondary barrier is pressed by using a heating skate plate or hot pad to cure the adhesive. A prior document related to the above-described installation process is disclosed in Korean Registration Patent No. 0928316.